DESCRIPTION: The long-term goal of this research is to understand the molecular mechanisms which bacteria use for cell-cell interactions. This proposal focuses on studying intercellular signaling of a model bacterium, Myxococcus xanthus. M. xanthus is a Gram-negative bacterium that exhibits a variety of multicellular behaviors. When deprived of nutrients, cells aggregate to form fruiting bodies, a process that involves chemotactic movement and intercellular signaling. Previous studies showed that developmental cells release chemoattractants during starvation and that the chemoattractants are sensed by chemosensory systems and relayed into the frz chemotaxis system. The objectives of the study are to find out the chemical natures of the developmental chemoattractants and to understand how the signal molecules are sensed by the chemosensory systems and relayed into the frz chemotaxis system. Described here are the genetic, molecular biological and biochemical methods to be used: 1) A set of mutants which fail to produce or sense the developmental chemoattractants will be isolated and characterized. 2) The interesting mutation genes will be cloned and sequenced; the regulation of gene expression will be studied. 3) The biochemical properties of the gene products will be studied with emphasis on the functions for producing or sensing developmental chemoattractants; extracellular matrix of developmental cells will be collected and fractionated for the developmental chemoattractants. Knowledge of intercellular signaling of M. xanthus could give insights into signaling mechanisms of other biological systems.